As a result the defective points, which caused the crash on May 10, 2002, were missed by Railtrack and Jarvis, its contractors, the Health and Safety Executive said yesterday.

In its third report on the crash, the HSE blamed poor maintenance as a major factor in the derailment of a West Anglia Great Northern Train.

The HSE ruled out sabotage, which had been suggested by Jarvis as a possible factor in the crash in which one of the train's four coaches mounted a platform and was left wedged under a canopy. The accident, in which 76 people were also injured, happened at lunchtime.

According to the report: "Had it occurred at a time of day when the platforms were crowded, there could have been even more injuries and loss of life."

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British Transport Police is continuing its investigation and manslaughter charges remain a possibility.

This was the HSE's third progress report on the disaster. It will produce its final analysis when any legal proceedings have taken place.

The report identified the set of faulty points outside Potters Bar station which failed. They were found to be in a bad condition, with two sets of nuts missing and a bar badly worn.

According to the HSE they had been poorly maintained, and nearby points also had "maintenance deficiencies".

This, the HSE said, indicated a wider problem. The train itself was being driven normally and within the speed limit for the track.

Jarvis was also accused of failing to have a proper understanding of the safety requirements for the maintenance, set up and inspection of the points. The HSE also found confusion over who was responsible for ensuring the work was done.

Louise Christian, the solicitor acting for five of the seven bereaved families, called on Alistair Darling, the Transport Secretary, to order a public inquiry.

"The report demonstrates in graphic terms that a decaying rail infrastructure with damaged safety critical parts is not subject to proper monitoring, maintenance or replacement."

James Clappison, Conservative MP for Hertsmere, whose constituency includes Potters Bar, described the report as "very worrying".

He added: "It is a catalogue of things which have gone wrong. We need a full public inquiry to establish the state of affairs that led to this. Unlike previous accidents, nobody has accepted responsibility for the disaster. Somebody should come forward and do so."

In a statement Jarvis said it noted the observations and recommendations in the HSE report. The company denied that it had failed to maintain the points which it and Railtrack inspected seven weeks before the crash.

"The investigation has yet to establish what happened in the seven weeks between the inspection and May 10. Therefore it is still uncertain as to what happened to cause the points to fail so catastrophically."

A spokesman for Network Rail, the non-profit body which has taken over responsibility for infrastructure from Railtrack, said that under a new programme it was putting into place, it would have more control over maintenance.